Meaning of special characters in help docs?

Question

For example, in this help page about finding and replacing with gsub() in awk:

I know now that the [ ] used in [, t] means that t is an optional argument, but I only know this now because my colleague told me. He did not know where he learnt this, my guess is that there are some commonly used conventions that help pages follow but I lack the vocabulary to be able to search for such conventions.

What other common formatting conventions are used when it comes to help pages? Where can I find out about them?

Answer 1

What you are looking for is called Command description syntax on Wikipedia or Utility argument syntax in The Open Group Base Specifications.